The Metrology Institute of Japan (MIJ), in cooperation with the Metrology Management Division, International Metrology Cooperation Office and Metrology Training Center, conducts research and development towards the establishment of primary standards (measurement standards), and dissemination of the measurement standards to societies and industries. It also carries out technological tasks to link the national measurement standards with those of other countries. At the same time, MIJ performs tasks for the government to maintain the accuracy of measuring instruments (specified measuring instruments) necessary for all types of business, taxation, safety and regulations.

The measurement standards consist of seven base units as shown in Fig.1, and derived units are formed as products of powers of the base units. MIJ collaborates with other countries and develops global mechanisms to maintain the equivalence of the measurement standards among domestic and international users. (traceability and mutual recognition arrangement: Fig.2)

With increasing awareness of environmental issues, requests for trace components analyses are increasing. However, the reliability of those analytical results is being questioned. To establish the reliability of analytical results, it is essential to use certified reference materials in which the matrix compositions are similar to those of actual environmental samples, such as sediments and river water, and concentration of trace components are certified. MIJ develops and provides certified reference materials such as sediment reference materials in which the certified values are given for environmental pollutants, such as harmful metals, organotins and polychlorinated biphenyls (PCBs).

Ear thermometers are novel thermometers sensing infrared radiation emitted by the human body. They are being widely used at airport facilities of various countries to test for SARS infection in individuals. The photograph shows the standard blackbody system for the calibration of ear thermometers developed by MD. It is a transportable high-accuracy standard blackbody system that was supplied to overseas institutes such as those in Singapore, and its use contributed effectively to prevention of a SARS epidemic in Asian countries.

The spectral database compiles information on six standard spectra (infrared, nuclear magnetic resonance (two types), mass, electron spin resonance and Raman spectra) of approximately 30,300 chemical compounds. These spectra have been collected since the 1980s and the data have been made available on the internet freely since 1997. They are frequently accessed globally. (http://www.aist.go.jp/RIODB/SDBSI)

Gamma-ray and X-ray are used in the vicinity of nuclear facilities, and for medical diagnosis and therapy; it is important to measure these rays accurately to ensure human safety and health. National standards for gamma-ray are established using the graphite cavity ionization chamber shown in the photograph. The values of personal monitors used in the vicinity of facilities utilizing ionizing radiation are calibrated on the basis of the reference standards of MIJ.

Radio waves used in cell phones and wireless LANs became essential in daily life. It is necessary to utilize a space in which the minimum possible scattering and reflection of waves from the surroundings are ensured to enable accurate measurement of the strengths of electric and magnetic fields and standard antennas. An open-area test site is used as an outdoor measurement field for the frequencies from 30 MHz to 1 GHz. An electromagnetic anechoic chamber (24 m x 15 m x 9 m) with surrounding walls, a ceiling and a floor constructed as close to nonreflecting as possible, is used as an indoor measurement field for frequencies of up to 40 GHz.

The importance of flatness measurement is increasing in many fields, for example measurement of silicon wafers for semiconductors, hard disk substrates, glass for liquid crystal display, and so on. The instrument developed at MIJ measures flatness by comparing a specimen with a precisely polished reference optical flat using Fizeau interferometry. It has a 310-mm-diameter measurement area which covers a 12-inch silicon wafer.

High-accuracy angle measurements are required in places such as the arm joints of robots and the rotation mechanism of paper feeders of printers; rotary encoders are used in many of these places. To calibrate high-accuracy rotary encoders, MIJ succeeded in developing a rotary encoder angle self-calibration system with the world's highest accuracy, enabling calibration at an accuracy of approximately 0.01" using the equal division averaged method (Masuda-Kajitani method).
(Collaborative research with Shizuoka Institute of Science and Technology and University of Electro-Communications)

A pico-second thermoreflectance measurement system has been developed in order to measure thermal diffusivities of thin films thinner than 1 micrometer. A film face of a transparent substrate side is heated by a pico-second laser pulse. Heat generated by the pump laser pulse diffuses towards the front surface of the thin film. The temperature change on the front surface opposite to the heated area is measured by the reflected intensity of probe pico-second laser pulse. The heat diffusion across molybdenum thin films with thickness of 75, 120, and 200 nm has been observed successfully for the first time in the world. Based on this technique, MIJ are now developing the thin film thermal diffusivity standard and reference thin films for thermal diffusivity measurements.

For chemical analysis, traceability to the international system of units (SI) has become important. As methods considered to be potentially the primary methods of measurement in realizing traceability to SI, titrimetry, gravimetric analysis and coulometric titration play major roles, particularly in the field of inorganic analysis. For example, it is possible to directly compare moles by applying EDTA chelatometric titration to many inorganic standard solutions. Gravimetric analysis is ultimately traceable to Prototype Kilogram. Coulometric titration is based on Faraday's law; it is used to realize a mole using current and time without any reference material.

The thermal motion of atoms was the most significant factor limiting the accuracy of time standard. MIJ has developed a high-accuracy atomic clock the error of which is only 1 sec per 20 million years by freezing the motion of atoms using pressure generated by a laser beam. The high-accuracy atomic clock is used to monitor and calibrate the coordinated universal time, which is the foundation of today's time system.

The kilogram is the only SI base unit still defined by an artifact, the prototype of the kilogram. For replacing the present definition of the unit to an atomic mass standard that is traceable to the mass of a single ¹²C atom, the Avogadro constant is being determined at MIJ by the X-ray crystal density method. This method determines the Avogadro constant by absolute measurements of the lattice constant using an x-ray interferometer, density using an optical interferometer and molar mass using a mass spectrometer for an identical silicon crystal. To realize the new definition, the Avogadro constant must be determined with a reduced uncertainty. For this purpose, technologies that measure the lattice constant, density and molar mass more accurately are being developed.

A temperature scale exceeding 1000 °C is essential in the technological development in various fields such as space and aeronautical materials, nuclear materials, and nuclear fusion. Conventionally, temperature fixed points for realizing temperature scale has been defined up to approximately 1100 °C. MIJ is the first to realize fixed points of alloys of metal and carbon as temperature standards for temperature regions exceeding 3000 °C. In the photograph below, on the left, light is radiating from a black body into which a eutectic alloy of iridium and carbon is cast at its melting point, approximately 2300 °C. On the right, a radiation thermometer is calibrated based on the intensity of the radiation.

MIJ is developing a "liquid helium-free programmable Josephson voltage standard" using an NbN/TiN/NbN device that is operable at approximately 10 K using a small freezer as the next generation voltage standard. If this system is introduced, not only will liquid helium, which is essential in conventional systems, become unnecessary, but a substantial reduction in the price of the system and in the maintenance cost will be realized. In the near future, high-accuracy voltage standards can be generated solely based on the availability of a 100 V AC power source.